Method for washing fibrous material



Oct. 17, 1961 c. w. ZIES 3,004,376

METHOD FOR WASHING FIBROUS MATERIAL Filed March 20, 1957 5 Sheets-Sheet1 mmvro& Cam. W 2/55 Oct. 17, 1961 c. w. ZIES METHOD FOR WASHING FIBROUSMATERIAL 5 Sheets-Sheet 2 Filed March 20, 1957 I N V EN T015. 07/11.. W.2155 rraflurr-r Oct. 17, 1961 c. w. 2155 33,004,

V METHOD FOR WASHING FIBROUS MATERIAL Filed March 20, 1957 5Sheets-Sheet 3 INVENTQR. mm W 2/56 Oct. 17, 1961 c. w. ZIES 3,004,876

METHOD FOR WASHING FIBROUS MATERIAL Filed March 20, 1957 5 Sheets-Sheet4 INVENTQR. 61742 W. 2/56 arranwzys Oct. 17, 1961 c. w. ZIES 3,

METHOD FOR WASHING FIBROUS MATERIAL Filed March 20, 1957 5 Sheets-Sheet5 INVENTOR. 9m. W. Z/las BY 0% flaw 17770 ENE YJ before introductioninto the second .stage .press.

United States Patent 3,004,876 7 METHOD FOR WASHING FIBROUS MATERIALCarl 'W. Zies, 'Lakewood,"ohioyassignorto International BasicEconomyCorporation, 'New York, N.Y., 'acorporation of'New'York'Filed'Mar. 20, 1957, Ser. No. 647,276 5.Claims. =(Cl. 134-25) Thisinvention relates to novel .and improved methods for processingmaterialsinthe barrel .of a continuous mechanical screw-press by injecting liquidunder pressure thereinto and subsequently removing liquid therefrom.More particularly, this invention relates to novel and improved methodswhereby fibrous materials may be deliquified and washed under conditionsof highepressure multi-stage washing in a single continuous mechanicalscrew press. 7

In the pulp and paper field there is an ever increasingly acute problemin the removal of contaminating liquors from pulps prior to theproductionof paperfrom these pulps. Not-only are these liquors injuriousto the production of the subsequent papers, but their reclamation in aconcentrated form is presently impossible. .In many instances whereinthese liquors are recovered, .they have been emptied into nearbystreamssince the relatively low concentration of contaminating materialsin these liquors practical means for expressing liquids from fibrousmaterials.

It is further wellknown that theseliquids, for example black liquorsthat exist ina paperpulp mill, may be washed from fibers with excessivevolumes of water in equipment known as vacuum drum washers.

ln-the first-instance, meehanicalscrew presses now employed fordeliquifying of .fibrous .materials in .paper mills fall into twoclassifications; .the first classification consists of thosegpresseswhich candewater a 'fibrousmaterial to a pressed pulpcontainingapproximately 65% moisture. When presses .in thisclassification are -.employed, three or four different presses in.series normally constitute a .washsystem wherein fresh water is addedto the fiber material:ahead of, for example, the fourth press in theline. .The efiluent from this fourth press is then added to thefiberbeingconveyed to the thirdpress in the line,-and so onback to thefirst press, in an attempt to attain as'efiicient a washing as possiblewith the minimum amountof water. It .is apparent to those even unskilledin-theart thatsuch a series of .machines constitutes a high capitalinvestment in .an .efiort .to attain a certaindegree.ofwashingefi'iciency.

The second classification consists of those presses which can dewater afibrous material to approximately 40% moisture. One of wthesepressesalone is capable of removing approximately 70% of the contaminatingliquor from a fibrous material 'wherein higher degrees of removal ofcontaminants is required. Two different-presses in this classificationused in series constitutes-awash systern 'whereinfresh water is added tothe fiber material ahead of the second press in'the' line. When; forexample,

neutral sulphite semichemically digested :wood chips are being washed in:such a two-stage-wash system, -20 minutestime must be provided forthisfresh=water.to

become uniformly absorbed into-the first pressed-fibers The efliuentfromthis secondpress is then added to the fibers being conveyedto the-firstpress in the line. Again'in the case of neutral sulphite semichemicallydigested chips, 3060 minutes retention time should be permitted for3,004,876 Patented Oct. 17, 19.61

ice

.uniform diffusionof this dilute liquorinto the chips entering the first.press. Although-forheflicient washing .in-a two-stage system as above,a.considerableamountof time is required for diffusion of wash watersinto :the fibrous materials, the primary disadvantage of this systemliesin .theefiect of the two-stage pressing onthe quality" of the requiredto attain the removal of a high percentage of the liquors in the pulp.

The process about to be described and the novel.apparatus whereby it canbe accomplished permit, among other features, the inherent-advantagesofamulti-stage, counter current continuous mechanical screw presswashing without the disadvantagesof the numbers of-machines required forthis type of system and without theexcessive amount of water required inthe multi-stage,:rotary .vacuum drum washing system.

One object ofthis invention is to.provide.methods.for introducingoperating liquids under pressure into the workingconfines of the barrelofacontinuous mechanical screw press.

A further object of this invention is to obviate the necessity ofmultiple units in a multi-stage washing system.

A further object of this invention is to provide methods for washing ofliquors from fibrous materials with .a minimum amount of dilution water.

A further object'of this invention is tolprovide methods for introducinga working liquid or a digesting .liquorQ into a.preceding zone of amechanical screw press barrel and mechanically extracting .this sameliquid and/ or liquor in a. succeeding zone of the screw press barrel.

In the wood pulp industry, there are three general classifications of;pulps produced whereby the original wood in chip form 'is digested withchemical liquors prior to refining the digested wood into pulp form.These three general classifications are termed semichemical,

to .producehighyield sulfitepulp are confronted withlthe same problem.Thisproblemconsists of transporting the digested chips in a large volumeof 'the digestion liquor through pumpsv and pipelines,whichofnecessitymustbe "fabricated of non-corrosive material such asstainless steel because of :the'corrosive natureof-these liquors.

"These chips, still in the presence of corrosive liquors,

are'then refined in any one oftherefining systems conventionally used*for this purpose. This, "however, requires .fur-ther use of stainlesssteel pipelines, pumps, valves and stock chests.

A further object o'ftliisinventionis' to providemethods whereby fibrousaggregates, "as in digestedwood chips,

may be washe'dfree of their contaminating'and corrosive liquors directlyand in one single operation.

Gther objects and 'advantages'willbeapparentfrom a study of thefollowing description 'in conjunction with accompanying drawings inwhich;

FIG. 'l isaview partlyin verticalsection andpar tly in side elevation,showing a working assembly suitable foruse 'in'the performance oftheimetho'dsherein disclosed, including vertical and horizontal screwpressbarthe recovery of digestion, liquor (black liquor). the generaltype of apparatus is familiar to those skilled rels and associatedelements. For convenience in illustration, because the complete assemblyis extensive, several parts of said assembly have been cut away and areshown in FIGS. 1A and 1B as follows:

FIG. 1A is a drawing, partly in section and partly in side elevation,showing feeding anddriving mechanism for the vertical press barrel, theplane of separation between FIGS. '1 and 1A being along the broken lineA-A in both said figures;

FIG. 1B is a drawing, partly in section and partly in side elevation,showing driving mechanism for the horizontal barrel, and otherassociated elements, the line of separation between FIGS. 1 and 1B beingalong the plane BB in both said figures;

FIGS. 2, 3 and 4 are sectional views taken respectively on the lines 22,33 and 44 of 'FIG. I;

are shown, for example in U.S. Patent No. 2,471,920, granted May 31,1949 to Raymond T. Anderson.

Referring to the drawings, FIG. 1 shows a screw press assembly wherein amaterial such as neutral sulfite semichemically digested wood chips maybe processed for Since in the art, I will describe only briefly thebroad function and purpose of some of the main elements of thestructure.

The screw press (assembled views l,'1A and 1B) includes feeding means(FIG. 1A) comprising a horizontal rotatable shaft carrying a helicalworm 11, the shaft and worm being enclosed in a tubular housing 12which.

10 and 15. Shaft 10 is driven from cooperating sprockets 17 which inturn are driven by a motor, not shown.

Drive of shaft 10 does not require much power since loose materialismerely being advanced laterally into chute 14 where incipient pressurebegins to be applied.

Shaft 15 is. driven from motor 18 through a gear reduction train inhousing 19, and then through a worm and gear or a bevel gear and pinionto shaft 15, this driving gear. being conventional and therefore notshown.

. Forming a downward continuation of chute 14 is a vertical barrelsection 22 -(FIG. 1) coaxial and coextensive with chute 14. This barrelsection will be more explicitly described hereinbelow. Shaft 15continues downwardly through barrel section 22, and carries there on aplurality of screw hubs 24, 25, 26, 27, 28, 29 and 30, each having itsrespective helical screw flight thereon, .the periphery of whichclosely. approaches the inner face of the barrel wall. 1

At the lower end of the vertical barrel is an imperferate collar 23within which-the advancing material is compacted into a liquid-seal plugby gradually increasing viouslyrecognized in the art, for example bydecreasing 4 the pitch of screw flights 36 towards the left end, or byincreasing the shaft root diameter towards the left, or by restrictingthe escape opening within an automatic choke assembly 37. This automaticchoke assembly is not shown in detail, but structural features of onesuitable embodiment are well shown and described inU.S. Patent No.1,752,054 to Raymond T. Anderson. Briefly, rotation of a worm 38produces co-acting rotation of a peripheral gear which through theoperation of further cooperating parts results in the'constriction ofinner peripheral parts so as to produce a change in the diameter of achoke aperture somewhat similar to the operation of the so-called irisdiaphragm which is used in there is a short space .59 where the materialmovement some optical elements, for example certain camera lenses. Thedrive for shaft 35 is here located at its right end (FIG. =1B) andconsists of a motor 39 and a train of reduction gearing in housing 40.

'23 of the vertical barrel, and the horizontal barrel 34 with referenceto the wash' treatment of the material in the horizontal barrel;

The general structure of barrel zone 22 will be better understood byreference to prior patents to Raymond T. Anderson, including forexample, U.S. Patents Nos. 1,722,882, and 1,773,771; This verticalbarrel part is built up from an assembly of barrel bars 43, lying sideby side (FIG. 2) and all fitted together in keystone-like fashion,having V-shaped spring clips 44 therebetween, 'and .tightly maintainedby semicircular frame members 45 and 46 which in turn are clampedlongitudinally by bars 47, transversely retained by tie bolts 48.

The barrel bars 43 are disposed in such close mutual lateral contact asto prevent solid material from escaping radially outwardly therebetween,but to permit liquid to be squeezed through theminute interstices whenthe pressure is heavy. The spacesbetween the barrel bars may be adjusteddepending on the fibrous material being pressed. 4 7

Assume that black liquor-bearing digested chips are being forceddownwardly through barrelzone 22, as the pressure increases aconsiderable portion of the black liqnor is squeezed outwardly betweenthe barrel bars, and it flows down into a trough 49 whence it proceedsto the right (FIG. 1B) and through a discharge port 50, and itis thenimpelled through conduit 51 by a pump 52. This black liquor is fullstrength and proceeds to a temporary storage tank. This upper zone22 ofthe vertical barrel is sometimes referred to as a fpre-press or drainagezone.

, Zone 23 of the vertical barrel might 'be termed the sealing? zonesince no drainage occurs therefrom and the plug therein formed providesa liquid seal for liquids originating in thehorizontal barrel as willappear. In certain instances, it might be advantageous to'extend sealingzone 23 upwardly into the vertical prepress zone. In one instance thisextension of the sealing zone may be 'obtained by assembling twosemicylindrical portions of tubing in the lower section of prepress zone22 in place of the barrel bars norm-ally employed. This same effect maybe attained merely by using barrel bars in this same area withoutspacers between the bars;

At 'the' junction of the vertical and horizontal barrels shaft 35, screwflights 36, barrel bars 63, and spacers or clips 64. In the presentembodimentthis structure runs the full length of the barrel. A pair ofopposed knife bars 65 and 66 are provided, which are perforated atspaced longitudinal points for a purpose soon to appear.

I have provided means for injecting washing liquid into about'the righthalf portion of the horizontal barrel, such means comprising a pipe 68from a supply sourcetnot shown), a pump 69, and end header 74), a topmanifold 71, a 'bottom'manifol'd 72 and branch pipes 73 and '74constituting injection nozzles. "Each branchpipe feeds into a respectiveapertureextending radially inwardly through a knife bar, the disposalbeing such .that the liquid is discharged into the barrel near the shaftsurface. 'Each branch pipe is provided with a'valve 75 for possibleindividual control. The right portion of the horizontal barrel of thisembodiment may'therefore be'termed the wash liquid injection portion.

Continuing the present exemplification in which'wash water is to be usedfor providing a washing effect on'the digested wood chips beingcompressed,the water is introduced under pressure near theshaft,'between screw flights, and as the fiber bundles and water are"davance'd intothe next worm flight, the pressure of the worm .forcesthe water to move through'the compacted 'fiber'bundles towards theoutside of the barrel. As the water moves through the fiber bundles, itpicks up the black liquor which remained in the fiber bundles andtogether they are pressed out of the barrel. As shown in the drawing,the six injection zones represented by'the six upper-lower branchnozzles, cause this water washing operation to be repeated six times.This, of course, could be multiplied as many times as seems advisable ordesirable.

A deflecting shield 67 prevents the concentrated liquor issuing fromzone 22 from intermingling with washed liquors issuing from the washingsection of the horizontal barrel 66 and pressing section 34. Acollecting trough 79 collects liquors from the horizontal barrel whichissue from the screw press by means of pipes 76, and from this troughthey proceed to intermittent storage tanks (not shown). This arrangementof concentrated liquor and wash liquor separation is utilized wherein amulti-stage two-press system is employed. If a multi-stage singlepresssystem is employed, baflle hown in FIG. 1 for separation of concentratedliquor and wash liquor are not employed.

The fibrils continue onwardly in the barrel towards the automatic choke37 and the 'dischargepoint 41. In'its trip through the horizontal barrelthe material hasbeen simultaneously exposed to mechanical expression andwater washing, and each effect supplements the other. By controlling thetemperature within the barrel, which can be done by pressure controland/or supplemental heating means, along with the multi-stage washingmeans'thus provided, very eificient' washing of fiber bundles and fibersis attained.

In this new process it has been discovered that the amount of wash waterinjected into horizontal wash section 66 of FIG. 1 is completely pressedfrom the fiber bundles in the wash section and in the subsequent presssection 65 so that no more liquid as water remains with the fiberbundles than if the Water had' not been injected in the first place. Theinjection of wash water intothe screw press, therefore, does not lowerthe efliciency of mechanical expression of liquid from the'fibers. Bygreatly aiding in the removal of contaminating liquors,however, it doesgreatly increase the washing efliciency of the unit.

The apparatus above-described and shown in the drawings can be modifiedin varioushelpful ways for specific purposes merely 'by furtherconsideration of the operations already described. The vertical barrelor at least the drainage portion thereof may be made longer to providemore drainage space and more liquor removal during the preliminarypressure application. Since a wide range of fibrous materials can beprocessed in this apparatus, it is recognized that it will be desirabletoprepress a greater quantity of liquor from fibrous materials whichoriginally contain a greater quantityof liquor. For example, in

the vertical section.

FIG. 1.

using the apparatus and; means of this inventionfor washingofliquor'from kraft pulp, thesepulps contain-four times the amount ofliquor as does aneutral sulfite semichemical'di'gested chip. Therefore,an extended drainage portion in the verticalbarrel would" be desirable.

barrel injection sections may he, therefore, employed 'whereinmaterialsthat absorb wash liquids or give up liq- .uor' fractions withdiificulty' are being processed. In addition to arranging the drainageof the'horizontal barrelto meet specific requirements, the entirehorizontal barrel may be lengthened by '1 'to 3 feet, or more,.asrequired by materials that give up contained contaminants with difii-Byway of example, but not of limitation, neutral sulfite'semichemicallydigested aspen wood chips were processed in the apparatus .of thisinvention as illustrated in 1.6 pounds of .water were employed for everyone pound .of fiber on the oven dry weightbasis. The digested wood chipsprocessed contained 32.2% soluble solids on the dry weight basis. Afterprocessing through the apparatus of this invention .and Washed .with theaforementioned amount of water by means of this invention, the fiberbundles thus produced contained only '6;5%.soluble's0lids on a dryweightbasis. In a second control 'test another quantity of the same.neutral sulfite semichemically digested aspen wood chips were pressedin the mechanical screw press not employingthe novel washing means ofthis invention. The fiber. bundles from this control test contained11.75% soluble solids on the dry basis, or almost double the .quantityas that when the methods of this invention were practiced. Anothercontrol test was made wherein another sample of the same neutralsulphite semichemically digested aspen wood chips were mixed withthreeparts of water per part of oven dry fiber. This amount of water isalmost double that used in the washing text involving the-methods ofthis invention. These digested chips, along with the abundant amount ofwater mixed with them, were. pressed in a standard screw press. Thefibers issuing from the discharge of the screw press contained 8.82%soluble solids on the dry basis. This latter test demonstrates that evenwith'the use of almost double'the amount of Water as required when usingthe novel means of this invention, the washing efliciency when employingstandand screw presses known to the art is far less eflicient than whenemploying the means of this invention.

Further proof of the values of the methods of this invention may beillustrated by commercial scale tests conducted :on neutral sulphitesemichemically digested aspen wood chips that contained 60% moistureafter the digestion step. The contaminating'black'liquors with thesedigested chips contained 17.5% soluble solids or 940 .pounds of solublesolidsper oneton o'fdry weight soluble'free fiber. These neutralsulphite semichemically digested chips were pressed'in a standard screw.press like that illustrated in FIG. 1, but without employing the methodsand-means of this invention. In this test the chips were pressed tofiber bundles-containing 50% moisture. 'Under these conditionsthepressedpulp retained '540 pounds of soluble solids per oven-dry tonof solubles free fiber. The condition oven dry is usually'brieflycharacterizedas O.D.,andma y.be defined as moisture free pulp. In asecond test, 1.2-pounds of water for -each poundof 'oven dry solublesfree fiber was added continuously to the neutral sulphite semichemicallydigested .chips .prior-toitheir beingconveyed to therpress used above.This mixture of digested chips and wash water was likewise pressed tofiber bundles containing 50% moisture. These pressed fiber bundles thencontained 302 pounds of soluble solids per O.D. ton of solubles freefiber. A third test was conducted wherein the neutral sulphitesemichemically digested chips were pressed in a first stage press sothat the resultant fiber bundles contained 50% moisture. 1.2 pounds ofwater per pound of oven dry solubles free fiber was then continuouslyadded to the pressed fibers from the first press as they were beingconveyed to a second press. The second press operation was so conductedthat the fiber bundles were also pressed to a material containing 50%moisture. The resultant fiber bundles from this test contained only 250pounds of solubles per ton of D. solubles free fiber. A fourth test wasthen conducted employing the methods and means of this invention whereby1.2 pounds of water heated to a temperature of 150 was pumped into sixports of the horizontal barrel as illustrated by pipe lines 76, FIG. 1,per pound of oven dry solubles free fiber. The press was so operatedthat the resultant fiber bundles also contained 50% moisture.

. Under the conditions of this press, the resultant fiber bundlescontained 250 pounds of solubles per ton of CD. solubles free fiber. I

The above series of tests clearly indicate that through the use of themethods of this invention, one press when employing the wash systemdescribed in this invention, is as effective'as two presses in series.Further, two

presses in series require an appreciable'amount of time to permitdiffusion of wash water into the pulps being processed. On the otherhand, it has been discovered that the ditfusion of the wash waters intothe pulps under the methods and means of this invention is almostinstantaneous. This instantaneous diflusion is a result of maintaining amechanical pressure upon the materials in process, which permits a highhydrostatic head up to 1,000 p.s.i. on the wash Water being pumped intoand through the fiber bundles within the confines of the press barrel66, FIG. 1. This high hydrostatic head of wash water on the pulp inprocess not only permits an extremely rapid rate of diffusion of thewash water into the fiber bundles, but also permits the filling of voidsbetween fiber bundles withwater instead of air as the fiber bundlescontinue their passage along the horizontal barrel of the apparatus 7shown in FIG. 1.

By increasing the mechanical pressure exerted on the fiber bundles inthe horizontal section of the apparatus shown in FIG. 1, more moisturemay be pressed from the fiber bundles. For example, when this pressureis increased so that only 40% moisture remains with the fiber bundles,only 150 pounds of soluble solids per ton of 0D. solubles free fiberremains. Not only does this represent a greater removal of solublesolids than that attained in a two-stage press system, but also thesingle pressing has no deleterious effect upon the pulps subsequentlymade from the fibers.

Referring now to the embodiment shown in FIG. 5, I illustrateschematically an arrangement in'which the horizontal barrel is equippedwith alternate wash and drainage sections so arranged as to furnishdirect counter current washing within the same horizontal barrel. Theshowing of FIG. 5, while simply schematic, will be clearlyunderstandable to one now familiar with FIGS. 1 t0 4,

in view of the following description.

Neutral sulphite semichemically digested chips with black liquorentrained therein areintroduced into the 'vided with a shaft 53 havingscrew flights 54 thereon and is shown as having drainage sections 84, 85and 86 alternating with sections 87, 88, and '89 which are non-drainageor solid wall sections. Under the drainage sections are troughs 84a, 85aand 86a to catch theliquid pressed through the barrel bar interstices inthese drainage sections, Fresh wash water is advanced by pump 55 intowashing section 87 through one or more injection nozzles 90, and as thematerial in the barrel is impelled from right to left, this Wash waterwith some black liquor in solution is exuded through the barrel bars indrainage section 84 and drops into trough 84a from whence it is advancedby pump 56 through pipe 91 and through nozzles 92. This dilutewater-liquor solution pervades the material in wash section 88 andadvances to drainage section 85 from. whence it is expressed into trough85a. It will be obvious that as the liquid regresses from the left endtowards the right, in countercurrent relationship to the solid material,the liquid acquires a higher percentage of black liquor.

From trough 850 the liquid is advanced by pump 57 through line 93 intothe first wash section 89 at the entry end of the horizontal barrel, andagain it is carried one step to the left into drainage section 86audthen is squeezed into trough 86a. From trough 860, the liquor, nowhaving been considerably enriched with black liquor, is pumped throughpipe 94 by pump 58 to the original point of entry 81 of digested chips,and discharged into the feed conveyor 80. As previously indicated, afair proportion of the excess concentrated liquor is expressed in thetravel through the vertical barrel. This may be collected in a trough 95and pumped through pipe 96 by pump 61 to any convenient disposal point.

There are certain cases wherein commercial mills require an even morecomplete removal of soluble liquors than possible in a multi-stagewashing operation utilizing a single pressas described hereinabove whenpracticing the methods of this invention.

FIG. 6 is a schematic showing of a multi-stage, multipress washingsystem, although in this particular instance, for simplicity, two stagesare indicated in the drawing. Obviously the system can be enlarged toany extent desired by the use of additional units or stages.

Referring to FIG. 6, fresh water is pumped by pump P through pipe 100 towash section 101'ofthe second press enclosed in broken lines 102. Theefiluent from sections 101 and 103 is collected in drainage pan 104 andadvanced by pump P through pipe 105 to prepress section 106 of thevertical barrel. The liquors drained from section. 106 areintercepted'fby pan 107 and are advanced by pump P to the wash section108 of the press enclosed in broken lines 109, the first press in thisseries. The liquors collected in drain pan 112 from the wash and presssections 108 and 111 of this first press 109 are advanced by pump P frompan 112 through pipe 113 to vertical pre-press barrel 114.

The liquors collected in drain pan represent the total wash effluentfrom the multi-stage pressing system just described, and these liquorsare pumped by pump P to an evaporator or to any end use ormeans ofdisposal known in the art.

Each ofthe wash sections 101 and 108, for example, may represent anyplurality of stages, for example between two and twelve stages. Inaddition, and bearing in mind the embodiment shown in FIG. 5 andheretofore described, it is-apparent that each of the screw presses inthe present series (FIG. 6) may be equipped with a counterflowwashsystem within each press. A countercurrent, multi-stage washing would,of course, be more efiicient, than for example a pair of presses inseries with only single point introduction of wash water in each of thepresses. It 'will, therefore, be apparent to those skilled in the artthat by using the method and means disclosed in the presentspecification, multi-stage countercurrent washing is now possible byusing only one or two items of equipment under conditions such that aminimum amount of wash liquid is required to obtain a high degree ofwashing efiiciency. 1

It will be apparent from the foregoing to those acquainted with the artthat there are many specific arrangements within each continuousmechanical screw press and arrangements of two or more presses whichwill make possible the removal of a calculated amount of contaminatingliquors from any fibrous material under study. For example, it will beperfectly obvious to those acquainted with the art that wash liquids maybe pumped into either a vertical or a horizontal barrel at points otherthan through the knife bar lugs illustrated in FIG. 1. For example,water could be pumped into the barrel at any point on the periphery ofthe barrel, or it could be pumped to the barrel at either end of thebarrel, but, of course, preferably to the feed end of the barrel. Itwill, however, be apparent to those skilled in the art that the mostefficient use of wash liquors is only attained when these liquors arepumped to the innermost parts of the materials being processed in thebarrel of the screw press as is accomplished through the means andmethods of this invention.

Although examples to illustrate the methods of this invention have beendrawn from the pulp and paper field, these specific examples by no meanslimit the scope of this invention. These same principles may be appliedto any natural occurring or synthetic fibrous material. They may beapplied to any material so processed in a screw press which permits thedifiusion of liquid between the interstices of the material beingprocessed.

The processes described herein may be facilitated or accelerated bysubjecting the conglomerate mass of liquor-bearing material to plannedvariations in temperature as it moves through the horizontal barrel.Such variations may be achieved, for example, by injecting steam throughinjection nozzles similar to those shown herein for injecting washliquid, and the steam may be developed either at atmospheric pressure ormay be super-heated to higher temperatures and pressures. Since rates ofdiffusion are increased with temperature, the values of the methods andmeans of this application may be enhanced by conducting the washing thusattained at temperatures above room temperature. For example, because ofa mechanical pressure imposed upon the pulp Within the apparatus of FIG.1 and because of the hydrostatic pressures that may be employed, it mayattain values as high as 5,000 p.s.i. Water under these pressures may beheated above 212 for injection into the apparatus of this invention. Afurther illustration of the use of temperatures by injection of steam orsuper heated water by the methods and means of this invention may beillustrated by a commercial scale processing of waste papers fordispersion of asphalt bodies. By using the injection means of thisinvention, steam under 150 p.s.i. pressure has been injected into thevertical barrel of the apparatus shown in FIG. 1 to increase thetemperature of the waste paper pulp before it reaches the transitionsection 59 shown in FIG. 1. By this steam injection, a waste paper pulpinitially at 100 F. may be raised to a controlled temperature, forexample 165 to 200 F., depending upon the requirements of the subsequentoperations to be conducted in the horizontal barrel of the press.

The wash water temperature can also be varied, and additional injectionsof water at any desired temperature can be made at any desired pointsalong the barrel.

What I claim is:

1. A method of washing residual digestion liquor from a digested mass offibrous material, said method comprising passing said material throughan elongated enclosure from an entry end to a discharge end thereof,applying pressure continuously to the material in a direction adapted tosimultaneously compact the material and assist in moving it in thedirection aforesaid, arranging said enclosure into a series of operatingsections, each section consisting of a washing zone and a drainage zone,providing apertures in the enclosure wall in registry with each drainagezone, injecting liquid into each washing zone, collecting drained liquidwhich escapes through the apertures in each drainage zone, re-injectingthe collected liquid-liquor solution into a respective washing zone in asection nearer to the entry end of the enclosure whereby to establish aflow of washing liquid gradually increasing in liquor concentration in adirection counter to the direction of movement of the material beingwashed, prepressing the material to remove a relatively readilyremovable fraction of liquor from the material, continuously chargingthe prepressed material into said enclosure, and injecting into thematerial being prepressed the drainage liquid from a drainage zone ofsaid enclosure.

2. A method of washing residual digestion liquor from a digested mass offibrous material, said method comprising passing said material throughan elongated enclosure from an entry end to a discharge end thereof,applying pressure to the material in a direction adapted tosimultaneously compact the material and assist in moving it in thedirection aforesaid, injecting a wash liquid into a zone of saidenclosure near said entry end, said wash liquid being capable ofleaching out said liquor, injecting steam into said enclosure betweensaid entry end and the zone where said wash liquid is injected, andproviding drain apertures in a drainage wall portion of said enclosurethrough which the aforesaid pressure drives the solution of liquid andliquor.

3. A method as defined in claim 2 wherein said steam is at a pressurebetween atmospheric pressure and pounds per square inch.

4. A method as defined in claim 2 wherein said fibrous material israised to a temperature of between F. and 200 F. by said steaminjection.

5. A method of washing residual digestion liquor from a digested mass offibrous material, said method comprising passing said material throughan elongated enclosure from an entry end to a discharge end thereof,applying pressure continuously increasing to between 1000 p.s.i. and5000 p.s.i. to the material in a direction adapted to simultaneouslycompact the material and assist in moving it in the direction aforesaid,injecting a wash liquid into a zone of said enclosure near said entryend, said wash liquid being capable of leaching out said liquor, andproviding drain apertures in a drainage wall portion of said enclosurethrough which the aforesaid pressure drives the solution of liquid andliquor.

References Cited in the file of this patent UNITED STATES PATENTS604,348 Bussells May 17, 1898 1,933,609 Wagner Nov. 7, 1933 2,308,883Kettenbach Jan. 19, 1943 2,761,799 Schroeder Sept. 4, 1956 2,784,725Williams Mar. 12, 1957 FOREIGN PATENTS 128,065 Australia July 8, 1948

1. A METHOD OF WASHING RESIDUAL DIGESTION LIQUOR FROM A DIGESTED MASS OFFIBROUS MATERIAL, SAID METHOD COMPRISING PASSING SAID MATERIAL THROUGHAN ELONGATED ENCLOSURE FROM AN ENTRY END TO A DISCHARGE END THEREOF,APPLYING PRESSURE CONTINUOUSLY TO THE MATERIAL IN A DIRECTION ADAPTED TOSIMULTANEOUSLY COMPACT THE MATERIAL AND ASSIST IN MOVING IT IN THEDIRECTION AFORESAID, ARRANGING SAID ENCLOSURE INTO A SERIES OF OPERATINGSECTIONS, EACH SECTION CONSISTING OF A WASHING ZONE AND A DRAINAGE ZONE,PROVIDING APERTURES IN THE ENCLOSURE WALL IN REGISTRY WITH EACH DRAINAGEZONE, INJECTING LIQUID INTO EACH WASHING ZONE, COLLECTING DRAINED LIQUIDWHICH ESCAPES THROUGH THE APERTURES IN EACH DRAINAGE ZONE, RE-INJECTINGTHE COLLECTED LIQUID-LIQUOR SOLUTION INTO A RESPECTIVE WASHING ZONE IN ASECTION NEARER TO THE ENTRY END OF THE ENCLOSURE WHEREBY TO ESTABLISH AFLOW OF WASHING LIQUID GRADUALLY INCREASING IN LIQUOR CONCENTRATION IN ADIRECTION COUNTER TO THE DIRECTION OF MOVEMENT OF THE MATERIAL BEINGWASHED, PREPRESSING THE MATERIAL TO REMOVE A RELATIVELY READILYREMOVABLE FRACTION OF LIQUOR FROM THE MATERIAL, CONTINUOUSLY CHARGINGTHE PREPRESSED MATERIAL INTO SAID ENCLOSURE, AND INJECTING INTO THEMATERIAL BEING PREPRESSED THE DRAINAGE LIQUID FROM A DRAINAGE ZONE OFSAID ENCLOSURE.